In general, traffic is transmitted by selecting an optimal path having low path costs between two nodes in a communication network. When there are a plurality of optimal paths having the same cost, multi-path communication methods use the plurality of optimal paths to transmit traffic rather than selecting only one path.
As a representative example, there is a Multi-chassis LAG in which a link aggregation group (LAG) according to an IEEE 802.3ad standard that defines a link group between two nodes is extended to multiple nodes and the link group can connect with two or more adjacent nodes. U.S. Pat. No. 7,463,579 (2008 Dec. 9) discloses technology for setting LAG to two or more adjacent nodes.
There is an equal-cost multi-path (ECMP) function in an L3 routing protocol such as Open Shortest Path First (OSPF) and Intermediate System to Intermediate System (IS-IS). A Trill (spanning tree protocol), which is a protocol for efficiently building a large scale L2 network without a STP, also supports the ECMP.
A principle of such a multi-path communication is that traffic is equally transmitted to multiple paths in a distributed manner. This is for efficiently using network resources. However, under such a traffic load balancing principle, since traffic is transmitted to all paths even when the amount of traffic is small, there is room for improvement under current situations in which energy efficiency of an entire network is also important.